Heat exchanger for continuous treatment of fluent material



.1. E. LASCHlNGER HEAT EXCHANGER FOR CONTINUOUS TREATMENT OF FLUENTMATERIAL Flled March 27 1945 May 8, 11951 INVENTOR John E Jase/zingerPatented May 8, 1951 GFFICE HEAT EXCHANGER FOR CONTINUOUS TREATMENT OFFLUENT MATERIAL John Ernest Laschinger, Johannesburg, Transvaal, Unionof South Africa Application March 27, 1945, Serial No. 585,113 In theUnion of South Africa September 21, 1944 1 Claim. 1

This invention relates to heat exchangers for continuously effectingheat exchange to or from a stream of material that is fluent in bulk;such as granular solid material or material in which the characteristicsof a liquid are more highly developed.

The object of the invention is to approximate closely to the conditionthat every small element of the stream is equally exposed to the heatexchanging influence for an equal period of time; and thereby produce aproduct of a homogeneous character throughout, notwithstanding that thematerial, for instance vermiculite undergoing expansion, is sensitive toboth temperature and time of heating. The attainment of this object ispromoted by subdividing the stream into small batches which are passedthrough the heat exchanger successively and in isolation from oneanother and in equal time periods; and by frequently agitating thecontents of each batch in a manner calculated to give all its smallelements equal exposure to the heat exchanging influence.

A heat exchanger for the continuous treatment of material fluent in bulkcomprising a heat conductive rotatable drum which is impermeable to saidmaterial, means for keeping said drum at a predetermined temperature, aplurality of substantially semi-annular plates dividing each of theopposite longitudinal halves of said drum into a series ofsemi-circumferential compartments each of which is axially displacedfrom the cor responding compartment of the opposite series and is opentowards said compartment; a lifting member comprising a shelf which isfixed on the base and across the width of the trailing end of eachcompartment and whereon material after agitation and heat exchange indispersed condition in said compartment is collected and lifted as saidmember moves upward, a forwarding member comprising slanting walls atsaid trailing end of each compartment in advance of said shelf wherebysaid shelf will be positioned in the plane of the adjacent compartmentin the opposite half of said drum and said material lifted by said shelfwill be discharged on further movement of said drum directly into saidadjacent compartment, means for delivering said material into the firstcompartment of said drum once in every revolution thereof in successivebatches, and driving means for rotating said drum that each said batchis separately dispersed, agitated and subjected to heat exchange andthen transferred into the adjacent opposite compartment, progressivelyalong the whole of said drum; 'A feeding device places a single batch of.the

material in the first compartment of the series, once in everyrevolution of the'rotary conveyor; and each such single batch is passedthrough all the compartments of the series in succession, so thatassuming uniform rotation, each batch remains in the heat exchange zonefor the same period of time. Another result is that during the normaloperation of the heat exchanger the conveyor is always transporting anumber of batches.

The trailing end of each compartment forms a scoop that lifts the batchin the compartment when said trailing end is on the rising side of itsorbit; and each compartment is so shaped as to cause its batch, uponbeing thus raised, to fall out of and away from the compartment.

By keeping the batches small, the time periods of conveyance of theirconstituent small elements are approximated closely to that of thebatches themselves. The interruption of the relatively quiet heattransfer to or from the batches by a succession of falls causes all thesmall elements of each batch correspondingly to be subject to frequentchanges of position in the batch, which is conducive to equalizing theirexposure to the heat exchanging influence.

The importance of isolating the batches lies in preventing the smallelements of the batches from escaping from the control that determinestheir time period in the heat exchanger. The isolation is commenced bythe feeding means which may itself out the successive batches from thestream of material and which feeds one batch per revolution into theinitial compartment of the series. The isolation is thereaftermaintained by two means: firstly by the structure of the compartmentsbeing such as to isolate the batches while they are within thecompartments; and secondly by the means that prescribes the transferpaths for the batches while the latter are moving from each compartmentto the next of the series. These two means are interdependent; theirconstruction and arrangement being such that they co-operate with oneanother.

Regarding the construction of the compartments, they are preferablyformed in the known manner by structure on the interior of a rotatingdrum so that the latter forms partof the compartment structure and isavailable to conduct heat to or from the material in the compartments.The compartments thus constructed are of arcuate shape. Theircircumferential walls that divide one compartment from that 'or those oneither side of it or them in the axial direction positioned with itsaxis A horizontal.

are provided by annular partitions of plate material extending from thedrum wall towards the axis. The result in practice is that the compartrnents may be regarded as curved troughs with open mouths that aredirected towards the axis and are inverted once per revolution of thedrum. Each partition may approximate to a circular plate occupying mostof the cross section of the drum, and it is preferred to cut out thecentre of the plate, so that in all cases an end iew shows an open axialchannel extending completely through the drum; which channel is usefulfor such purposes as passing off moisture vaporized when the material isheated: for visual inspection of the material in the drum; and ifdesired for the introduction of heating gas or accommodating a radiatingelement As regards the structure that determines the transfer path alongwhich a batch is transferred from one compartment to the next advancedcompartment of the series, the means prescribing the transfer path isdivided into two parts, one of which imposes on the material undertransfer the axial or advancing component of its movement, and the otherof which controls the descent of the material and in particular socontrols it that the material can be poured as a more or less freecascade without danger of its being received into other than the nextadvanced compartment.

In general, the transfer path and the compartment structure are suchthat each batch, after being received in a compartment, remains on theorbital bottom of said compartment during a substantial part of therotation of the latter so that the batch is exposed to quiet heattransfer by contact with the outer wall; and so also that the relativemovement between compartment and batch causes a mild agitation of thebatch. The circumferential extent of the compartment structure is afactor in safeguarding isolation of each batch from all preceding orfollowing batches during the period of such relative movement.

An example of a heating furnace according to the invention for treatingfluent material is described with reference to the accompanying drawing,in which Figure l is a side elevation partly in section,

Figure 2 is a perspective view of the internal arrangement, with thedrum partly brolren away,

Figure 3 is a View seen in the direction of the axis of part of Figure2, and

Figure 4 is a developed View of the feed division and two compartmentsof the Figure 2 furnace.

In the drawings, 2 designates a drum barrel The drum is provided withcircular treads B rotatably supported on rollers C. The drum is rotatedconstantly in the direction of the arrow M by driving means G. Thebarrel of the drum 2 is enclosed within a furnace casing D and is heatedby fuel burnt at E in the lower part of the casing. Products ofcombustion pass away through the chimney F. The fluent material to besubjected to furnace treatment is fed by a launder l to a batch makingsection 5 of the drum at the feed end 5 thereof; and the treatedmaterial is gravitationally discharged from the delivery end i of thedrum to a receiver 8. I l designates a niunber of partitions providingcompartments extending in planes materially traverse to the axis A andspaced along the length of the drum.

The compartments above mentioned are provided by annular partition wallsI! with their central areas cut away at Ha.

In the interior of the furnace, there isa single cries of compartmentsindicated by 9a, 9b and so on. Each compartment is an open trough ofabout 180 circumferential extent; this being an extent that allows thefluent material fed into the furnace to lie for a period as a free massin the bottom of the compartment and in contact with the drum wall, asindicated at [0. While lying there the mass is not inert, but issubjected to advantageous agitation by the drag of the relatively movingdrum wall.

A pair of compartments is shown separately in Figure 4. The greater partof the circumferential extent of each compartment lies in a verticalplane, between the partition walls ll each of which is in a singlevertical plane; and the whole extent of that greater part is thusavailable, when at the lower position of its orbit, to receive materialpoured into it from a higher point in said plane. The scoop end l2 ofeach compartment is constituted partly by the shelf l3 that ispreferably tilted upwardly and inwardly with reference to the drum wallwhen on the rising side of the drum, and partly by the partition wallson each side of the shelf.

The direction of advance of the series is axial, and the magnitude ofeach step of advance is half the axial width of the compartments. Themeans for imparting this axial advance to the material is provided bythe trailing end l4 of each compartment, immediately before the liftingshelf l3. This trailing end is slanted forward with reference to thedirection of the rotation so as to bring the shelf [3 into the plane ofthe next compartment. That is to say, the shelf 53 of compartment 911 isin the plane of the greater part of compartment 91).

The batch making feed end 5 consists of a completely annular trough l5into which the spout l delivers constantly. At one circumferential pointof said trough is the scoop l6 that during its rotation gathers up, as asingle batch, all the material that has been fed into the trough duringa revolution; then, acting like the shelves l3 lifts the gathered batchand tips it to fall into the bottom of the first compartment 9a of theseries.

The batch remains in the bottom of said compartment 9a as indicated bylil, during a considerable part of one half revolution of the drum.Thereafter the walls ll of the slanting trough portion !4 come round andshift the batch axially forward, so that the batch is now in the planeof the next compartment 9!). Immediately thereafter the first shelf I3comes round and collects and raises the batch at the upgoing side of thedrum. As the trailing end of the compartment 9a turns over to about theposition shown in Figure 2, the batch begins to shower out of saidtrailing end and falls into the right-plane portion of the next trough9b which is then vertically under it. In order to confine the cascadingmaterial within the vertical planes limiting said right-plane portion,the shelf i3 is made wholly parallel with the axis.

The batch remains in compartment 9b, sliding in the bottom portionthereof, until the shelf at the trailing end of compartment 9b in turncomes round and begins to lift the batch. While this has been going onanother batch has been collected. in I5 and is cascaded into the firstcompartment So at the moment that the first batch begins to fall fromsaid shelf at the trailing end of compartment 91), and into the bottomof compartment 3c.

The means prescribing the isolating transfer 5 path are thus incombination, the long circumferential extent of each of two consecutivecompartments: the slanted portion l4; and the arrangement of the shelfI3 that causes the batch to fall in the plane of the greater part of thenext following compartment.

A fresh batch is formed and delivered to the first compartment once perrevolution of the drum; so that during the regular operation of thefurnace, all the compartments which are in the angular position in whichthey can be occupied are occupied, each with its separate batch.

I claim:

A heat exchanger for the continuous treatment of material fluent in bulkcomprising a heat conductive rotatable drum which is impermeable to saidmaterial, means for keeping said drum at a predetermined temperature, aplurality of substantially semi-annular plates dividing each of theopposite longitudinal halves of said drum in- I 6 shelf whereby saidshelf will be positioned in the plane of the adjacent compartment in theopposite half of said drum and said material lifted by said shelf willbe discharged on further movement of said drum directly into saidadjacent compartment, means for delivering said material into the firstcompartment of said drum once in every revolution thereof in successivebatches, and driving means for rotating said drum so that each saidbatch is separately dispersed, agitated and subjected to heat exchangeand then transferred into the adjacent opposite compartment,progressively along the whole of said drum.

JOHN ERNEST LASCHINGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,518,938 Nielsen Dec. 9, 19241,734,571 Godfrey Nov. 5, 1929 2,063,446 Lanzi et a1 Dec. 8, 19362,279,362 Baker Apr. 14, 1942 FOREIGN PATENTS Number Country Date 20,943Great Britain Sept. 13, 1909 of 1909

